docs: def new_multigraph(self, name, data=None, **attr):
          """Return a new instance of type MultiGraph, initialized with the given
          data if provided.
  
          :arg name: a name for the graph
          :arg data: dictionary or NetworkX graph object providing initial state
  
          """
          self._init_graph(name, 'MultiGraph')
          mg = MultiGraph(self, name, data, **attr)
          self._graph_objs[name] = mg
          return mg